1. Field of the Invention
The present invention relates to a vertical axis wind turbine blade, especially to a vertical axis wind turbine blade that prevents wind power applied to an upwind surface and a downwind surface at the same time so as to increase the power generation efficiency of the wind turbine.
2. Description of Related Art
Generally, a wind turbine set uses wind-wheels to receive wind power and then convert the wind power to electricity. Now a vertical wind turbine is used to convert kinetic energy from air to mechanical energy and transmit the mechanical energy to generator sets for electricity production. A plurality of helical blades is connected to a rotor. By the design of the blades, wind acts on the blades to drive the rotor and the rotor is connected to generator sets. As a result, the kinetic energy of the air is converted to electric power. However, helical blades of the vertical axis wind turbines available now include upwind surfaces and downwind surfaces and the resistance over the whole downwind surface caused by wind is quite large. Thus the resistance is opposite to the pushing force over the whole upwind surface caused by wind and the opposing forces cancel each other partially. Therefore the power generation efficiency of the wind turbine is lowered.